Controlled engine exhaust gas recirculation is a known technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to atmosphere. A typical EGR system comprises an EGR valve that is controlled in accordance with engine operating conditions to regulate the amount of engine exhaust gas that is recirculated to the fuel-air flow entering the engine for combustion so as to limit the peak combustion temperature and hence reduce the formation of oxides of nitrogen.
Exhaust emission requirements have been imposing increasingly stringent demands on tailpipe emissions that may be met by improved control of EGR valves. An electromagnetically operated actuator controlled by an engine management computer is one device for obtaining improved EGR valve control. It is known to associate such a valve with an engine intake manifold to dope the induction flow before the flow passes to runners to each individual cylinders.
It is also known to provide each cylinder with a strictly mechanical mechanism to recirculate exhaust gas from a cylinder back to the intake of the cylinder.